Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts

Details Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts

2012-03-12

arxiv.org/abs/1203.2621v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

23 pages, 17 figures, Submitted to A&A

Scientific paper

We investigate the evolution of galactic disks in N-body Tree-SPH simulations. We find that disks, initially truncated at three scale-lengths, can triple their radial extent, solely driven by secular evolution. Both Type I (single exponential) and Type II (down-bending) observed disk surface-brightness profiles can be explained by our findings. We relate these results to the strong angular momentum outward transfer, resulting from torques and radial migration associated with multiple patterns, such as central bars and spiral waves of different multiplicity. We show that even for stars ending up on cold orbits, the changes in angular momentum exhibit complex structure as a function of radius, unlike the expected effect of transient spirals alone. Focussing on one of our models, we find evidence for non-linear coupling among m=1, 2, 3 and 4 density waves, where m is the pattern multiplicity. We suggest that the naturally occurring larger resonance widths at galactic radii beyond four scale-lengths may have profound consequences on the formation and location of breaks in disk density profiles, provided spirals are present at such large distances. We also consider the effect of gas inflow and show that when in-plane smooth gas accretion of ~5 M_sun/yr is included, the outer disks become more unstable, leading to a strong increase in the stellar velocity dispersion. This, in turn, causes the formation of a Type III (up-bending) profile in the old stellar population. We propose that observations of Type III surface brightness profiles, combined with an up-turn in the stellar velocity dispersions beyond the disk break, could be a signature of ongoing gas-accretion. The results of this study suggest that disk outskirts comprised of stars migrated from the inner disk would have relatively large radial velocity dispersions, and significant thickness when seen edge-on. [Abridged]

Affiliated with

Also associated with

No associations

Rating

Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution of Galactic Disks: Multiple Patterns, Radial Migration and Disk Outskirts will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-142240